In general, in reading out data in the EEPROM (Electrically Erasable Programmable Read Only Memory) cell, the sensing speed depends on the threshold voltage in the memory cell.
There happens a case in which the threshold voltage of the completed memory cell is higher than the threshold voltage of the memory cell in design due to the variations in the process conditions while manufacturing the memory cell. In case of reading out data which are stored in such memory cell, some drawbacks requiring to redesign the sense amplifier or to use various options are occurred because the sensing speed varies.